Systems and methods for doctor blade load and vibration measurement as well as blade vibration mitigation
A doctor blade cartridge for use in a doctor blade holder is disclosed. The doctor blade cartridge is for receiving a doctor blade, and includes at least one blade supporting member, wherein the blade supporting member is sufficiently stiff to support the doctor blade and includes load indication means for providing a signal indicative of at least one of blade supporting member strain and blade supporting member deflection.
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The present application claims priority to U.S. Patent Application Ser. No. 61/816,318 filed Apr. 26, 2013, the disclosure of which is hereby incorporated by reference in its entirety.
BACKGROUNDThis invention generally relates to doctoring systems, and relates in particular to doctor blade holders that provide improved performance of doctoring systems during the production of tissue and paper.
While efforts have been made to measure doctor blade loads in order to provide improved performance of doctoring systems, such measurements of doctor blade loads have conventionally been limited to measuring applied cylinder load, such as disclosed in U.S. Pat. No. 5,783,042. These measurements represent the total applied load to the doctor, and therefore the average reaction load at the blade tip. This measurement however, has several shortcomings. First, the measurement is representative of the blade load component considered normal to the dryer (Yankee) surface, and thus does not accurately represent the load that is tangential to the dryer surface, that load being more representative of friction and other blade-surface interface behavior. Second, the measurement does not represent the variation in the blade load that exists lengthwise along the dryer face width. Third, the total applied cylinder load also includes contributions from various other factors such as weight unbalance moment and bearing friction, and therefore a fraction of the measured cylinder load represents the blade load.
In certain applications, it is desired to provide improved reliability in Yankee coating and creping systems within the tissue industry. In such applications, it is sometimes desired to monitor numerous coating and creping parameters. In tissue production for example, the conventional Yankee doctor blade carrier includes a cartridge, as disclosed in U.S. Pat. No. 5,066,364. Conventional techniques for providing vibration measurements in such systems have typically involved mounting sensors on the doctor beam. These locations however, are removed from the blade tip, and thus unique vibration signatures that may be present in the blade tip that may go undetected.
There remains a need therefore, for doctor blade holders that provide improved performance, particularly for the production of tissue and paper.
SUMMARYIn accordance with certain embodiments, the invention provides a doctor blade cartridge for use in a doctor blade holder. The doctor blade cartridge is for receiving a doctor blade and includes at least one blade supporting member. The blade supporting member is sufficiently stiff to support the doctor blade and includes load indication means for providing a signal indicative of at least one of blade supporting member strain and blade supporting member deflection.
In accordance with another embodiment, the invention provides a doctor blade cartridge for use in a doctor blade holder, and the doctor blade cartridge is for receiving a doctor blade and includes at least one blade supporting member. The at least one blade supporting member is sufficiently stiff to support the doctor blade and includes vibration measurement means for providing a vibration signal indicative of vibration of the at least one blade supporting member.
In accordance with a further embodiment, the invention provides a doctor blade cartridge for use in a doctor blade holder, wherein the doctor blade cartridge is for receiving a doctor blade and includes at least one blade support member that is sufficiently stiff to support the doctor blade and includes damping means for reducing blade vibration.
The following description may be further understood with reference to the accompanying drawings in which:
The drawings are shown for illustrative purposes only and are not necessarily to scale.
DETAILED DESCRIPTIONIn accordance with certain embodiments, the present invention facilitates the measurement of blade load and blade vibration during the production of tissue and paper, as well as the reduction of blade vibration during the production of tissue and paper. As mentioned above, the conventional Yankee doctor blade carrier includes a cartridge for receiving and supporting the doctor blade as disclosed for example, in U.S. Pat. No. 5,066,364, the disclosure of which is hereby incorporated by reference in its entirety. Such a cartridge is generally comprised of two side walls that sandwich a row of spacers, and the spacers provide the load support points for the blade. A doctor blade is received within the cartridge of the doctor blade holder.
In accordance with certain embodiments, a sensor measurement point is located directly at the blade support, affording very accurate load and vibration measurements associated with blade behavior. In particular, in certain embodiments the conventional spacer component is replaced with a blade supporting member (e.g., a beam component), uniquely designed to simultaneously achieve the necessary stiffness for proper dynamic performance of the doctor blade (e.g., creping blade or cleaning blade), and adequate deflection such that a structural parameter such as strain or deflection or vibration may be measured.
As further shown in
In particular,
The beam 26 of
The doctor blade 14 rests on the support surfaces 32, which would be narrow in length such that as wear took place, the load would still be primarily applied to the beam midspan. The surfaces 32 could be hardened via heat treatment, or a hard coat such as Electroless Nickel coating could be applied. This would promote life of the support surface and thus beam life. The underside 42 is straight, which may be a requirement for certain fiber optic cables 44, but is also suitable for strain gage applications as well.
In the embodiment shown in
In accordance with another embodiment, a blade supporting beam 60 may include midspan depression surfaces 62, as well as an opening 64 in the portion that provides the support surface 66 for supporting the doctor blade. Since the target location for maximum strain measurement is at the midspan, this beam profile may allow higher strain to be achieved at the midspan, without detrimental compromise in stiffness. Support hole 68 and slot 70 dictate the active beam length Lb. On the underside of the beam as shown at 72, a groove 74 may be machined in the beam for application and anchoring of the fiber optic cable, and fiber optic strain sensor 76. The bottom surface is otherwise flat, so as to avoid bend radii in the fiber optic sensor and cable.
Another beam variation is shown in
In both the cases of the fiber optic sensor system, and strain gage sensor system, not only can the average value of load be measured, but data acquisition sampling rates can be high to allow dynamic measurements as well. In the case of the fiber optic sensor, the commercially available sampling rate is as high as 1000 samples per second, providing a frequency spectrum available of up to approaching 500 Hz. In the case of the strain gage, data acquisition is available for sample rates up to 100,000 samples per second, providing much that a broader frequency spectrum may be obtained with strain gages. The load frequency spectrum may offer great insight in establishing process load signatures.
Another beam variation that utilizes an alternative sensing means is shown in
In the manufacturing process of pneumatic beam 100 of
With reference to
It is also preferred that upstream valve 124 be large enough so that sonic conditions prevail at discharge gap 116, rather than at restrictor 128. The resulting relationship between pressure at 130 and blade load at surface 106 will approach linear over most of the load range. If sonic conditions were allowed to prevail at restrictor 128, then the relationship between pressure at 130 and blade load at surface 106 would be significantly nonlinear. A linear relationship is much preferred for sensing purposes. In various embodiments, the sensing may be achieved upstream of the beam (e.g., at valve 124 or restrictor 128) or downstream as air exits the gap 116.
The pneumatic beam load measurements will be limited to an average load value or dynamic measurements up to very low frequency at best. This is because of the slow response of the pneumatic system, as compared with the fast response of the fiber optic system and the strain gage system.
The ambient temperature is in the vicinity of 200° F.-250° F. typically, and the beam metal temperature will be that as well. The typical temperature of the air supply will be much less, more typically 80° F.-100° F. total temperature at the upstream source. At the discharge at gap 116, the static temperature will decrease further owing to the high velocity and adiabatic expansion.
This could result in a significant temperature gradient across the lever thickness as suggested in
To mitigate this distortion, a low expansion alloy 200 may be applied to an underside surface 202 of the blade supporting beam 100 of
In accordance with another embodiment of the invention a piezoelectric dynamic strain gage may be used.
In accordance with further embodiments of the present invention, a blade supporting member may be provided in the form of a circular spacer that includes viscoelastic material. For example,
With respect to the use of viscoelastic damping illustrated in
In accordance with further embodiments, doctor blade holder cartridge may be provided that includes any or all of the blade supporting members discussed above to provide strain sensors and displacement sensors as well as vibration detection and damping.
Those skilled in the art will appreciate that numerous modifications and variations may be made to the above disclosed embodiments without departing from the spirit and scope of the present invention.
Claims
1. A doctor blade cartridge for use in a doctor blade holder, said doctor blade cartridge for receiving a doctor blade, said doctor blade cartridge including at least one blade supporting member, wherein said blade supporting member is sufficiently stiff to support the doctor blade and includes load indication means for providing a signal indicative of at least one of blade supporting member strain and blade supporting member deflection, wherein said doctor blade cartridge includes a plurality of blade supporting members.
2. The doctor blade cartridge as claimed in claim 1, wherein said at least one blade supporting member is a beam.
3. The doctor blade cartridge as claimed in claim 2, wherein said load indication means includes a fiber optic strain sensor for sensing strain.
4. The doctor blade cartridge as claimed in claim 2, wherein said load indication means includes a strain gage strain sensor for sensing strain.
5. The doctor blade cartridge as claimed in claim 2, wherein said load indication means includes lever means for permitting blade load to regulate flow through a variable discharge restrictor.
6. The doctor blade cartridge as claimed in claim 5, wherein said lever means causes upstream pressure to vary approximately linearly with load.
7. The doctor blade cartridge as claimed in claim 5, wherein said lever means includes a bimetallic member to compensate for thermal distortion.
8. The doctor blade cartridge as claimed in claim 5, wherein said lever means includes a thermal coating barrier on a surface thereof to create more uniform temperature and reduce distortion.
9. The doctor blade cartridge as claimed in claim 2, wherein said beam includes a support area for contacting the doctor blade, and wherein said support area is approximately mid-distance between a pair of support mounts by which the beam is attached to the doctor blade cartridge.
10. The doctor blade cartridge as claimed in claim 1, wherein said doctor blade cartridge includes passage means for providing passage of any signal cables and fluid carrying tubes away from the doctor blade cartridge.
11. The doctor blade cartridge as claimed in claim 10, wherein said passage means includes openings within the at least one blade supporting member.
12. A doctor blade cartridge for use in a doctor blade holder, said doctor blade cartridge for receiving a doctor blade, said doctor blade cartridge including at least one blade supporting member, wherein said blade supporting member is sufficiently stiff to support the doctor blade and includes load indication means for providing a signal indicative of at least one of blade supporting member strain and blade supporting member deflection, wherein said at least one blade supporting member is a beam.
13. The doctor blade cartridge as claimed in claim 12, wherein said doctor blade cartridge includes a plurality of blade supporting members.
14. The doctor blade cartridge as claimed in claim 12, wherein said load indication means includes a fiber optic strain sensor for sensing strain.
15. The doctor blade cartridge as claimed in claim 12, wherein said load indication means includes a strain gage strain sensor for sensing strain.
16. The doctor blade cartridge as claimed in claim 12, wherein said doctor blade cartridge includes passage means for providing passage of any signal cables and fluid carrying tubes away from the doctor blade cartridge.
17. The doctor blade cartridge as claimed in claim 16, wherein said passage means includes openings within the at least one blade supporting member.
18. The doctor blade cartridge as claimed in claim 12, wherein said beam includes a support area for contacting the doctor blade, and wherein said support area is approximately mid-distance between a pair of support mounts by which the beam is attached to the doctor blade cartridge.
19. The doctor blade cartridge as claimed in claim 12, wherein said load indication means includes lever means for permitting blade load to regulate flow through a variable discharge restrictor.
20. The doctor blade cartridge as claimed in claim 19, wherein said lever means causes upstream pressure to vary approximately linearly with load.
21. The doctor blade cartridge as claimed in claim 19, wherein said lever means includes a bimetallic member to compensate for thermal distortion.
22. The doctor blade cartridge as claimed in claim 19, wherein said lever means includes a thermal coating barrier on a surface thereof to create more uniform temperature and reduce distortion.
23. A doctor blade cartridge for use in a doctor blade holder, said doctor blade cartridge for receiving a doctor blade, said doctor blade cartridge including at least one blade supporting member, wherein said blade supporting member is sufficiently stiff to support the doctor blade and includes load indication means for providing a signal indicative of at least one of blade supporting member strain and blade supporting member deflection, wherein said doctor blade cartridge includes passage means for providing passage of any signal cables and fluid carrying tubes away from the doctor blade cartridge.
24. The doctor blade cartridge as claimed in claim 23, wherein said doctor blade cartridge indicates a plurality of blade supporting members.
25. The doctor blade cartridge as claimed in claim 23, wherein said beam includes a support area for contacting the doctor blade, and wherein said support area is approximately mid-distance between a pair of support mounts by which the beam is attached to the doctor blade cartridge.
26. The doctor blade cartridge as claimed in claim 23, wherein said passage means includes openings within the at least one blade supporting member.
27. The doctor blade cartridge as claimed in claim 23, wherein said at least one blade supporting member is a beam.
28. The doctor blade cartridge as claimed in claim 27, wherein said load indication means includes a fiber optic strain sensor for sensing strain.
29. The doctor blade cartridge as claimed in claim 27, wherein said load indication means includes a strain gage strain sensor for sensing strain.
30. The doctor blade cartridge as claimed in claim 27, wherein said load indication means includes lever means for permitting blade load to regulate flow through a variable discharge restrictor.
31. The doctor blade cartridge as claimed in claim 30, wherein said lever means causes upstream pressure to vary approximately linearly with load.
32. The doctor blade cartridge as claimed in claim 30, wherein said lever means includes a bimetallic member to compensate for thermal distortion.
33. The doctor blade cartridge as claimed in claim 30, wherein said lever means includes a thermal coating barrier on a surface thereof to create more uniform temperature and reduce distortion.
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- International Search Report and Written Opinion mailed on Sep. 1, 2014 in connection with International Application PCT/US14/035668, 13 pages.
- International Preliminary Report on Patentability mailed on Nov. 5, 2015 in connection with related International application No. PCT/US2014/035668, 10 pages.
Type: Grant
Filed: Apr 28, 2014
Date of Patent: Nov 29, 2016
Patent Publication Number: 20150075742
Assignee: Kadant, Inc. (Westford, MA)
Inventors: Robert P. Johnson (Sutton, MA), Allen Brauns (Sturbridge, MA)
Primary Examiner: Mark Halpern
Application Number: 14/263,335
International Classification: D21G 7/00 (20060101); D21G 3/00 (20060101); D21G 3/04 (20060101);